This invention relates to mechanisms for manipulating sections of pipe to form drill strings, and particularly to a mechanism for holding a section of the drill pipe and for loosening the threaded connection between sections of the drill pipe.
Blast hole drills and other similar drilling rigs use drill strings that are made up of drill pipes that are threaded end to end. In adding to and removing pipe from the drill string, it is necessary to hold sections of pipe against rotation. A tool wrench is typically employed for that purpose.
One form of tool wrench engages flats on a drill pipe much like that of an open-end wrench engaging a bolt or nut. To engage this form of wrench, the drill operator is required to rotate the drill pipe until the flats on the drill pipe are aligned with the wrench. At this point, the wrench is slid over the flats on the drill pipe. The operator then turns the drill pipe and the wrench until the wrench hits stops provided on the mast drill deck.
In another form of tool wrench, slots are provided in the drill pipe that are engaged by pawls on the ends of wrench arms. The slots allow 40.degree. of pipe rotation in either a clockwise or counterclockwise direction. A further form of tool wrench uses individually spring-loaded pawls.
In adding or removing pipe from the drill string, it is also necessary to provide a mechanical assist to loosen the threaded connection between sections of pipe. This is typically accomplished using a casing tong that grips and rotates one section of the pipe while the adjacent section is held against rotation by the tool wrench.
A common form of power operated drill pipe tong includes hydraulic cylinder assemblies for moving jaws into engagement with a pipe joint. Cylinder assemblies are also provided to afford a torquing action to make up or break apart a drill string. In many instances problems arise as sufficient torque cannot be applied because the force applied by the hydraulic cylinder on a jaw of the casing tong is in a single direction.
I provide a casing tong which can be extended from and retracted to a stored position and also affect a unique push-pull action on the drill pipe joint.